Plectranthus amboinicus (Lour.) Spreng, growing in Malaysia and India, is a decorative medicinal herb commonly cultivated by ordinary families. The medicinal part of Plectranthus amboinicus is the epigeal portion. Plectranthus amboinicus is also known as Cuban oregano, Indian borage, Indian mint, Mexican mint, Mexican oregano or Spanish thyme. East Indians use Plectranthus amboinicus as a fabric aromatic, and the English discovered its attractive fragrance when importing shawl fabrics from India in the 1820's. When the Plectranthus amboinicus leaves are put directly with clothing, it not only has an aromatic effect, but also prevents the clothing from being eaten by moths. It is thought to be useful for disinfection, enhancing sexual excitement and preventing insect bites. In addition, Plectranthus amboinicus may be used for treating poisonous snake bites and relieving symptoms such as headache, flatulence, vomiting, diarrhea and fever. Moreover, Plectranthus amboinicus oil is a popular perfume in Asia, and it is used in aromatherapy for improving epithelia regeneration, treating acne, and relieving the symptoms of eczema, Athlete's foot and dry cracked skin. Furthermore, Plectranthus amboinicus is a good tranquilizer and aphrodisiac that can relieve anxiety and enhance sexual desire.
Various uses of Plectranthus amboinicus are reported in general magazines, but scientific studies on Plectranthus amboinicus are rarely seen in literature. US 2006/0099283 A1 discloses leaf juice of Plectranthus amboinicus for treating cancer and/or tumor. U.S. Ser. No. 11/605,178, a patent application relating to the present invention, provides a pharmaceutical composition comprising a therapeutically effective amount of Plectranthus amboinicus crude extracts/extracts and a therapeutically effective amount of Centella asiatica Urban extracts.
Centella asiatica Urban (pennywort) is a plant naturally growing in the coastal areas of Madagascar and the Indian Ocean. The medicinal part of Centella asiatica Urban of the Apiaceae family is its dried whole plant. Centella asiatica Urban is also known as European water-marvel, Gotu kola, Kola, Indian pennywort, Indian ginseng, Horse-hoof grass, Pegaga, Mandookaparni, Tiger herbal, Spadeleaf, or Tono. For hundreds of years, Centella asiatica Urban has been thought to be useful in the traditional medicine of Asia for improving wound healing. The extracts of Centella asiatica Urban comprise two major compounds: asiaticoside and madecassic acid. Centella asiatica Urban extracts are used to treat burns and trauma and prevent postoperative adhesion, and the preparation methods of Centella asiatica Urban extracts have been described in some patent applications. For example, U.S. Pat. No. 4,318,906 and CN 1353972A disclose the medical uses of Centella asiatica Urban as the single active ingredient; U.S. Pat. Nos. 6,475,536, 6,267,996, CN 1313124A, CN 93110425.4 and CN 1089497A disclose the use of Centella asiatica Urban in combination with other substances for cosmetic formulation, treating burns or making ointment for trauma; and U.S. Pat. Nos. 5,834,437, 6,417,349 and CN 1194154A disclose the methods for preparing Centella asiatica Urban extracts.
Conventional separation processes for separating the components from the mixture include contacting the mixture with a nonionic absorbing resin such as DIAION® HP20, DIAION® HP20SS, Sepabeads® SP207 (Mitsubishi Chemical Corporation), Amberlite™ XAD-2 (Rohm and Hass company), Amberlite™ XAD-4, and the like. The steps comprise packing the nonionic absorbing resin into a separation column, adding the mixture to the column, and eluting the column with a solvent. When such process is taken to treat a massive amount of a mixture, it is time-consuming and the elution conditions are not easily controlled.
The leaf juice of US 2006/0099283 A1 was obtained by grinding and removing tissue fragments and/or residues, and the different fractions of the leaf juice were separated with centrifugal filter devices.
The Plectranthus amboinicus extracts of U.S. Ser. No. 11/605,178 were prepared by utilizing a series of solvents with different polarities to elute the extracts from a chromatographic column. This method is complicated and time-consuming. There is still a need to provide a method for obtaining in large quantities the active ingredients of Plectranthus amboinicus. 
Surprisingly, we found that a stirring method can replace the traditional column separation method and be used for mass production of Plectranthus amboinicus extracts. The stirring method is fast and the elution conditions can be easily controlled. Moreover, Plectranthus amboinicus extracts obtained by stirring separation are more effective than extracts prepared by column chromatographic separation.